Honeywell 4073 issues

Hari · Jan 4, 2019

Hi Guys,

I'm a complete novice trying to figure out a problem with my central heating/hot water.

Problem is that I'm getting HW when the programmer is set to CH ONLY. HW ONLY seems to be just fine (complete opposite of what most folk seem to have a problem with.)

I've got what looks to be a Y plan system with a Honeywell 4073 3-port valve with genuine Honeywell actuator fitted.

I've taken a look inside the actuator which seems to respond to all three possible positions as instructed by the programmer when powered up.

I've checked the valve spindle and it seems to be moving fairly freely (by hand). Although it has just a small range of movement, you can sense the rubber ball closing off the valves at each extreme of movement.

Can anyone think of a reason why hot water is still passing the valve and heading to the water heating tank?

Thank you!

Riley · Jan 4, 2019

I’d be definitely questioning if the valve is closing off properly.

Hari · Jan 4, 2019

Thanks for getting back to me Riley. Really appreciate that...

From the little bit of reading around I've done and from your suggestion, I reckon this must be a physical problem in the valve (a bad seal being made due to internal gunk or a worn rubber ball).

From what I can work out from the electrical operation and switching system, the actuator is making that final connection to the orange wire that finally activates the boiler in the CH ONLY mode. Like you've said, that valve must not be closing off properly, it's just that the actuator thinks that it has...

I'll leave this here for any other rookies like myself looking for the sequencing and electrical info: Y Plan central heating system

Chuck · Jan 4, 2019

It's not uncommon for the balls to fail on these valves. There was a time that Honeywell supplied service kits but I'm not sure whether these are still available. Many pro's would just replace the whole thing; you can waste a lot of time fiddling with these things and success is not assured.